Influence of high concentrations of mineral salts on production process and NaCl accumulation by Salicornia europaea plants as a constituent of the LSS phototroph link

Use of halophytes (salt-tolerant vegetation), in a particular vegetable Salicornia europaea plants which are capable of utilizing NaCl in rather high concentrations, is one of possible means of NaCl incorporation into mass exchange of bioregenerative life support systems. In preliminary experiments it was shown that S. europaea plants, basically, could grow on urine pretreated with physicochemical processing and urease-enzyme decomposing of urea with the subsequent ammonia distillation. But at the same time inhibition of the growth process of the plants was observed. The purpose of the given work was to find out the influence of excessive quantities of some mineral elements contained in products of physicochemical processing of urine on the production process and NaCl accumulation by S. europaea plants. As the content of mineral salts in the human liquid wastes (urine) changed within certain limits, two variants of experimental solutions were examined. In the first variant, the concentration of mineral salts was equivalent to the minimum salt content in the urine and was: K – 1.5g/l, P – 0.5g/l, S – 0.5g/l, Mg – 0.07g/l, Ca – 0.2g/l. In the second experimental variant, the content of mineral salts corresponded to the maximum salt content in urine and was the following: K – 3.0g/l, P – 0.7g/l, S – 1.2g/l, Mg – 0.2g/l, Ca – 0.97g/l. As the control, the Tokarev nutrient solution containing nitrogen in the form of a urea, and the Knop nutrient solution with nitrogen in the nitrate form were used. N quantity in all four variants made up 177mg/l. Air temperature was 24°C, illumination was continuous. Light intensity was 690μmol/m2s of photosynthetically active radiation. NaCl concentration in solutions was 1%. Our researches showed that the dry aboveground biomass of an average plant of the first variant practically did not differ from the control and totaled 11g. In the second variant, S. europaea productivity decreased and the dry aboveground biomass of an average plant totaled 8g. The increase of K quantity in the experimental solutions resulted in an elevated content of the element in the plants. The increase of K uptake in the second experimental variant was accompanied by a 30–50% decrease of Na content in comparison with the other variants. Comparative Na content in the other variants was practically identical. N, Mg and P content in the control and experimental variants was also practically identical. The increase of S quantity in the second experimental variant also increased S uptake by the plants. But Ca quantity, accumulated in aboveground plants biomass in the experimental variants was lower than in the control. NaCl uptake by plants, depending on the concentration of mineral salts in the experimental solutions, ranged from 8g (maximum salt content) up to 15g (minimum salt content) on a plant growth area that totaled 0.032m2.